diff --git a/scheme/ikarus.boot.prebuilt b/scheme/ikarus.boot.prebuilt
index 480deae..7c2dadc 100644
Binary files a/scheme/ikarus.boot.prebuilt and b/scheme/ikarus.boot.prebuilt differ
diff --git a/scheme/ikarus.io.ss b/scheme/ikarus.io.ss
index 9203db2..c679bd7 100644
--- a/scheme/ikarus.io.ss
+++ b/scheme/ikarus.io.ss
@@ -70,6 +70,7 @@
     accept-connection accept-connection-nonblocking
     close-tcp-server-socket 
     register-callback
+    input-socket-buffer-size output-socket-buffer-size
     )
 
   
@@ -129,6 +130,7 @@
       accept-connection accept-connection-nonblocking
       close-tcp-server-socket 
       register-callback
+      input-socket-buffer-size output-socket-buffer-size
       ))
 
   (module UNSAFE  
@@ -1238,6 +1240,26 @@
   (define input-file-buffer-size (+ input-block-size 128))
   (define output-file-buffer-size output-block-size)
 
+  (define input-socket-buffer-size 
+    (make-parameter (+ input-block-size 128)
+      (lambda (x) 
+        (import (ikarus system $fx))
+        (if (and (fixnum? x) ($fx>= x 128))
+            x
+            (error 'input-socket-buffer-size 
+              "buffer size should be a fixnum >= 128"
+              x)))))
+
+  (define output-socket-buffer-size 
+    (make-parameter output-block-size
+      (lambda (x) 
+        (import (ikarus system $fx))
+        (if (and (fixnum? x) ($fx> x 0))
+            x
+            (error 'output-socket-buffer-size 
+              "buffer size should be a positive fixnum"
+              x)))))
+
   (define (fh->input-port fd id size transcoder close who)
     (letrec ([port
               ($make-port 
@@ -2110,9 +2132,9 @@
             (set-fd-nonblocking socket who id))
           (values 
             (fh->output-port socket
-               id output-file-buffer-size #f close who)
+               id (output-socket-buffer-size) #f close who)
             (fh->input-port socket
-               id input-file-buffer-size #f close who)))))
+               id (input-socket-buffer-size) #f close who)))))
 
   (define-syntax define-connector 
     (syntax-rules ()
diff --git a/scheme/last-revision b/scheme/last-revision
index cd3f37d..b9f85c2 100644
--- a/scheme/last-revision
+++ b/scheme/last-revision
@@ -1 +1 @@
-1445
+1446
diff --git a/scheme/makefile.ss b/scheme/makefile.ss
index bb5624f..89f9e9d 100755
--- a/scheme/makefile.ss
+++ b/scheme/makefile.ss
@@ -1405,10 +1405,13 @@
     [accept-connection-nonblocking    i]
     [close-tcp-server-socket          i]
     [register-callback                i]
-    [&i/o-would-block                 i]
-    [make-i/o-would-block-condition   i]
-    [i/o-would-block-condition?       i]
-    [i/o-would-block-port             i]
+    [input-socket-buffer-size         i]
+    [output-socket-buffer-size        i]
+
+    ;[&i/o-would-block                 i]
+    ;[make-i/o-would-block-condition   i]
+    ;[i/o-would-block-condition?       i]
+    ;[i/o-would-block-port             i]
     [ellipsis-map ]
     [scc-letrec i]
     [optimize-cp i]
diff --git a/scheme/pass-specify-rep-primops.ss b/scheme/pass-specify-rep-primops.ss
index 8c05c6b..c0c76dc 100644
--- a/scheme/pass-specify-rep-primops.ss
+++ b/scheme/pass-specify-rep-primops.ss
@@ -2170,7 +2170,7 @@
   [(V x i) 
    (prm 'sll
      (prm 'logand
-          (prm 'mref (T x)
+          (prm 'bref (T x)
                (prm 'int+
                     (prm 'sra (T i) (K fx-shift))
                     (K (- disp-code-data vector-tag))))
diff --git a/scheme/tests/bytevectors.ss b/scheme/tests/bytevectors.ss
index 0f10776..d57bda4 100644
--- a/scheme/tests/bytevectors.ss
+++ b/scheme/tests/bytevectors.ss
@@ -373,6 +373,13 @@
        (bytevector-s64-native-ref bv 8))]
 
 
+    [(lambda (x) (= x 73))
+     (let ([sz (- (* 10 4096) 8)])
+       (import (ikarus system $bytevectors))
+       (let ([bv (make-bytevector sz)])
+         (bytevector-u8-set! bv (- sz 1) 73)
+         (collect)
+         ($bytevector-u8-ref bv (- sz 1))))]
 
     ))